Quantum Simulation of Interacting Spin Models with Trapped Ions
Quantum Simulation of Interacting Spin Models with Trapped Ions
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2012
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通讯作者：
K. Islam
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作者：
K. Islam
Kazi Rajibul Islam，博士，2012马里兰大学物理系和国家标准与技术研究所联合量子研究所复杂多体系统的量子模拟有望理解强相关系统（如高tc超导体和自旋液体）涌现特性的起源。冷原子系统由于其优异的量子相干性、初始化和读出特性以及支持多种形式的相互作用的能力，为量子模拟提供了一个几乎理想的平台。在本文中，我介绍了在横向磁场存在下的远程Ising模型的量子模拟实验，其中有多达16个超冷171Yb离子链被捕获在线性射频保罗阱中。每个171Yb离子中的两个超精细能级作为自旋1/2体系。我们通过观察具有单位点分辨率的状态依赖荧光来检测单个离子的自旋态，并且可以直接测量任何可能的自旋相关函数。自旋-自旋相互作用是通过应用来自精确调谐激光的偶极子力来设计的，这些激光的节拍音符诱导受激拉曼跃迁，几乎耦合到离子运动的集体声子模式。伊辛耦合在符号和强度上都受到有效横向场的控制，并被绝热操纵以研究该自旋模型的各个方面，例如基态中量子相变的出现和由于竞争的反铁磁相互作用而引起的自旋受挫。自旋受挫通常会在基态中产生大量简并，从而导致自旋系统中的纠缠。我们在一个三自旋系统中检测并表征了这种挫折诱导的纠缠，证明了挫折和纠缠之间的第一个直接实验联系。对于较大数量的自旋，我们还通过适当的激光调谐来改变反铁磁耦合的范围，并观察到较长距离的相互作用降低了激发能，从而破坏了基态秩序。这个系统有可能被放大，以研究大范围的具有几十个自旋的全连接自旋网络，在经典计算机上，潜在的理论变得难以处理。捕获离子相互作用自旋模型的量子模拟
Title of dissertation: QUANTUM SIMULATION OF INTERACTING SPIN MODELS WITH TRAPPED IONS Kazi Rajibul Islam, Doctor of Philosophy, 2012 Dissertation directed by: Professor Christopher Monroe Joint Quantum Institute, University of Maryland Department of Physics and National Institute of Standards and Technology The quantum simulation of complex many body systems holds promise for understanding the origin of emergent properties of strongly correlated systems, such as high-Tc superconductors and spin liquids. Cold atomic systems provide an almost ideal platform for quantum simulation due to their excellent quantum coherence, initialization and readout properties, and their ability to support several forms of interactions. In this thesis, I present experiments on the quantum simulation of long range Ising models in the presence of transverse magnetic fields with a chain of up to sixteen ultracold 171Yb ions trapped in a linear radiofrequency Paul trap. Two hyperfine levels in each of the 171Yb ions serve as the spin-1/2 systems. We detect the spin states of the individual ions by observing state-dependent fluorescence with single site resolution, and can directly measure any possible spin correlation function. The spin-spin interactions are engineered by applying dipole forces from precisely tuned lasers whose beatnotes induce stimulated Raman transitions that couple virtually to collective phonon modes of the ion motion. The Ising couplings are controlled, both in sign and strength with respect to the effective transverse field, and adiabatically manipulated to study various aspects of this spin model, such as the emergence of a quantum phase transition in the ground state and spin frustration due to competing antiferromagnetic interactions. Spin frustration often gives rise to a massive degeneracy in the ground state, which can lead to entanglement in the spin system. We detect and characterize this frustration induced entanglement in a system of three spins, demonstrating the first direct experimental connection between frustration and entanglement. With larger numbers of spins we also vary the range of the antiferromagnetic couplings through appropriate laser tunings and observe that longer range interactions reduce the excitation energy and thereby frustrate the ground state order. This system can potentially be scaled up to study a wide range of fully connected spin networks with a few dozens of spins, where the underlying theory becomes intractable on a classical computer. Quantum Simulation of Interacting Spin Models with Trapped Ions